Electric plate-condenser.



G. SEIBT.

ELECTRIC PLATE CONDENSER.

APPLICATION FILED 00117, I911.

1,155,448. Patented Oct. 5,1915.

2 SHEETS-SHEET I.

\\III\IIIIIIIII III/ IIII IIIII 0 I WITNESSES: lNl/E/VTOR BY 2 dZTTORNEY G. SEIBT.

ELECTRIC PLATE CONDENSER.

APPLICATION FILED OCT. 17, I911.

1,155,448. Patented Oct. 5, 1915.

2 SHEETSSHEET 2.

f1 f a}; i 6.

A TTORNEY UNITED STATESi'PATENT OFFICE.

GEOBG SEIBT, OF SCHONETBERG, NEAR BERLIN, GERMANY, ASSIGNOR '10 GENERALTRANSMISSION COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

ELECTRIC PLATE-CONDENSER.

Application filed October 17, 1911.

To all whom it may concern:

Be it known that I, GEORG SEIBT, a subject of the German Emperor,andresident of Schiineberg, near Berlin, Germany, have invented certainnew and useful Improvetype, WhlChare widely used, especially in wirelesstelegraphy, comprise two sets of parallel semicircular plates, one setbelng stationary and the other mounted to turn so as to bring the platesof the movable set, to

a greater or smaller extent, between the plates of the stationary set,thereby varying the capacity of the apparatus.

, In the practical use of condensers of this type, as made hitherto,considerable difficulty has been experienced in obtaining a uniformefficiency under different atmospheric conditions, particularly as itproved necessary to employa large amount of time and skill in order toobtain perfectly plane plates of even thickness and even spacing.Furthermore, the apparatus was of comparatively large dimensions. 7 a

By means of my invention, more fully described hereinafter, I have beenenabled to reduce considerably the size of a condenser of a givencapacity and to insure a permanently eflicient operation of theapparatus.

The invention will now be described in detail with reference to theaccompanying drawings, in which Figure l is a top view of the apparatus;

Fig. 2 .is a central vertical section on line 22 of Fig. 1; Fig. 3 anelevation andFig. 4 a top view of the blank from which the movablemember or electrode of the condenser is made; Fig.5 is a face view andFig. 6 a top view of the finished movable member (without its shaft orspindle); Fig. 7 is a sec tional view of the cutter employed for millingout the spaces of the condenser members; Figs. 8 and 9" are a face Viewand a top view respectively showing a portion of the stationarycondenser member or electrode at an intermediate stage of itsmanufacture; and Figs. 10 and 11 are similar views of the completedstationary member. For making the inner or movable member of thecondenser, the following procedure Specification of Letters Patent.

Patented oct. 5, 1915.

Serial No. 655,210.

has been devised after considerable experimenting: I start with twoblanks of the shape shown in Figs. 3 and 4 and of suitable material,such as magnalium or aluminium. Each of these blanks has the form of asolid half cylinder with faces 7, which are made perfectly plane bymeans of cutters or other suitable tools, and with axial projections orstuds 8 at opposite ends. The two blanks are fitted against each otherwith the plane surfaces f and held in this positionby means of aclamping ring surrounding the two blanks. The composite cylindrical bodythus formed is placed in a lathe and the studs 8 are turned to a conicalshape. Suitable fitting or collars are then applied to the ends or studs8 so as to enable the clamping ring to be removed and yet hold the twoblanks together. The body with its fittings is then placed in the latheand the cylindrical surface turned down to theproper diameter. Then bymeans of a chisel I cut into the periphery shallow grooves which shouldbe somewhat narrower than the intended distance between the finishedplates 6. The cylindrical body is then fitted into a suitable socket tohold it together, the fit-v tings previously applied to the studs 8 areremoved, the studs chiseled off, and the body is drilled throughaxially. The socket having been removed, the two blanks fall apart, andeach of them receives in its axial groove a, ashaft or spindle b securedto the blank by means of screws 0.

It will be understood, of course, that the two blanks are used in theassembling of two condensers.

The next operation consists in working the grooves or intervals to theproper width and depth, with such accuracy that the material remainingbetween the cuts will form absolutely plane and parallel plates spaced,with perfect uniformity. For this purpose I employ a lathe having a veryaccurate micrometer scale in connection with the adjusting spindle ofthe slide rest. On this slide rest I' provide a bracket with twobearings, parallel to the lathe spindle, and in these bearings I mount adouble milling cutter of the shape shown in Fig. 7. The teeth of thecutter should be backed off considerably. to prevent the plates fromyielding laterally. The distance (1 equals the desired thickness of theplates, and the distance d should be will not rub against the plates.lVhile the work is being rotated by the lathe, the double cutter is alsorotated in any suitable manner, as by means of a driving belt, or byhand.

The micrometer adjustment insures a perfectly regular spacing ofadjacent plates. If the tool is accurate and the scale reliable, thevariations will be but small fractions of a tenth of a millimeter.

The manufacture of the stationary outer member has been carried outsuccessfully by either one of the following two methods: the firstmethod is very similar to that described above for the manufacture ofthe inner, movable member. The blank in this case is a-half cylinder ofa larger diameter than the blank employed for the movable member. 'Thisblank is turned so that its circumference will be part of a truecylinder, in the same manner as described above, and formed with anaxial groove of a sufficient diameter to receive the central portion orcore 6 of the movable member. Then, instead of employing a chisel togroove the stationary member, I clamp the latter securely on a supportor table, start the grooves on the inner periphery of the member with apreliminary milling cutter, and.

finish these grooves to the accurate dimensions desired, by means of themilling cutter shown in Fig. 7.

The second method is as follows: a hollow cylindrical body is firsttrued on its inner and outer surfaces, and by means of a turning chiselor other suitable tool annular grooves g of a few millimeters depth arecut in the inner surface, as shown in Fig. 8, so as to form ridges itwhich constitute distance pieces, and a body 11 forming a carrier. Thegrooves g are spaced evenly, by the aid of a micrometer adjustment forthe chisel. The hollow cylinder is then cut into two half-cylinders (orif it was formed of two half-cylinders soldered together for the truingand grooving operations, they are unsoldered). The segmental plates j,produced separatelyin any suitable manner, are then slipped into thegrooves g and secured by riveting at their ends, by soldering, or bymeans of a retaining strip 76 (Figs. 10 and 11) or in any other approvedmanner. The

plates, being of a relatively small diameter and distance pieces. Whenproduced according to the second method, the stationary member may besaid to comprise as integral parts, 1, the carrier 2' and 2, thedistance pieces h, the plates 7' in this case not being integral withthe carrier and the distance lGCeS.

The plates, both of the movable member and of the stationary member,were made about 2 millimeters thick in a condenser having a normalcapacity of 2000 centimeters, and the width of the air gaps remainingbetween a plate of one member and the adjacent plates of the othermember, was only about from .25 to 3 of a millimeter, that is'to say,considerably less than what has been found necessary in practice priorto my invention, when air gaps were generally given a width of about1.25 of a millimeter (50/1000ths of an inch). With sixteen plates ineach set, I obtained the same capacity which hitherto was formed by aKopsel condenser with twenty-four plates to each set, a plate thicknessof 1 millimeter, and an external diameter of 15 centimeters against 9centimeters in my case. The greater thickness and smaller diameter ofthe plates employed by me give them much greater rigidity, so thatwarping of the plates or deflection by jarring, and resulting contact,are avoided efficiently. Since the carrier and the distance pieces forman integral body (and the plates also, in two of my constructionsdescribed above), the spacing of the plates is absolutely invariable.The particular method of insuring an even spacing of the plates alsoinsures absolute uniformity of the air gap, so that an eflicientcondenser is obtained notwithstand ing its relatively small dimensions.The fact that the plates, the distance pieces, and the carrier, or atleast two of these three elements, are formed or machined from the samepiece of metal insures an invariable position of the plates relativelyto each other and avoids the drawbacks resulting from a relativeshifting of the plates.

The two condenser members made in the manner described above, areassembled to form a condenser structure, for instance according to Figs.1 and 2. The lower portion of the spindle b is journaled in a metalbushing Z fitted into an insulating collar m, preferably made ofBakelite, which is secured by means of screws 12. to a stationary bottomplate 0 secured rigidly to the carrier portion 73 of the stationarycondenser member A. To the lower end of the spindle b is secured asegmental counterweight p, on the side opposite to the movable condensermember B, so as to balance the same. This counterweight is arranged toswing in a plane below the bottom plate 0, so that the latter will notrestrict the movement of the condenser member 13.. The upper portion ofthe spindle b is journaled in metal bushing Z fitted into an insulating(Bakelite) collar m which is secured by means of screws 11, to the cover10 secured rigidly to the carried portion 71 of the stationary condensermember A. On the (metal) cover p I place a hard rubber plate p providedwith a graduation on which is adapted to indicate the pointer g securedrigidly to the spindle b. For this purpose, the pointer is formed at oneend with a sleeve 9 surrounding the spindle b and screwed into a hardrubber knob 1' which is held rigidly on the spindle b by means of a setscrew r. The cover 72 has a threaded projection or stufling box p onwhich screws a cap 79 arranged to press against an insulating (Bakelite)collar m which is separated from the collar m by acompressible packingor washer s.

In order to lock the movable. member B after it has been adjusted byturning the knob 1', the following arrangement is provided: The upperend of the spindle b is made with an axial bore at the lower end ofwhich .is a transverse through aperture in which are located two smallsteel blocks t ture of the condenser members as described adapted to beshifted outward and to be pressed against the bushing Z so firmly as tolock the spindle against'rotation. This is accomplished by thewedge-shaped lower end of the pin it which engages both blocks t, saidpin screwing into the axial bore of the spindle and being provided witha hard rubber head u, for turning it.

The dial plate p is secured to the cover 79'. by means of screws 1)which extend into posts 'v-the lower ends of which are secured by screws2) ma base plate 1?.

The electrical connections to the condenser members are made in anysuitable manner. The binding post 20 for thestationary member A issimply secured to the cover 7), in metallic contact therewith. Thebinding post 'w for the movable member B is fitted into an insulatingsleeve to extending through the plate 79 and cover 1), also through aninsulating plate e0 secured to the cover p by screws 10*, and through aconducting strip 10 secured to the plate 'w by a short screw to and byone of the nuts w on the lower end of the binding post w. The bindingpost w and the conducting strip to are thus insulated from thestationary member of the apparatus. To the flange at the inner end ofthe strip w is secured the outer end of a spring 10 (preferably made ofsilver) coiled around a sleeve 1) secured to the spindle b the inner endof the spring being secured to said sleeve. The movable member B thusremains in electrical connection with the binding post-w notwithstandinany movement of said member about the axls b. A stop 7) may be providedon the inside of the cover p to limit the swinging movement of themember B.

In order to prevent the entrance of dust and moisture, the two condensermembers are inclosed in a metal casing comprising a cylindrical body :1with afiange m at the upper end, and a dished bottom :6 provided at itscenter with a perforated plug 00 normally closed by a screw cap w. Aclamping collar 3 screwing on the cover p has a flange y adapted topress the flange an upward against a washer z engaging the cover p.This, in connection with the stufling box 10 (packing 8) through whichthe spindle 2) extends, efiieiently seals the working parts of thecondenser against the entrance of moisture or dust.

For the purpose of securing a more gradual change of capacity as themovable member B enters into the spaces between the plates 7' of thestationary member A, the plates 6 of the movable member may be beveledoff stepwise as indicated in Fig. 6, so that such plates, being thus ofdifferent extent circumferentially, will enter successively between theplates j of the stationary member.

It will be observed that inthe manufacherein, the cutting of the slitsinto the solid body,'to-'form plates between the slits, is carried outin aplurality of stages, a prehminary operation serving to locate orroughly prepare the grooves or slits while a final or finishingoperation gives them the exact dimensions desired. Also the cuttingoperation as described progresses from one end of the bodv to the other,the milling cutters operating successively at difi'erent portions of thebody. A very important advantage is due to the cutting of at least twoslits at a time, since by such procedure I avoid all bending strains onthe plate remainirw between the two disks of the cutter, each diskbacking or bracing such plate against the bending action exerted by theother disk.

Various modifications may be made without departing from the nature ofmy invention as set forth in the appended claims.

I claim:

1. In an electric condenser of the type having arallel plates, acondenser member comprislng parallel plates, and a carrier for saidplates. said carrier and plates being integral with one another andmachined from a single metallic body.

2. In an electric condenser of the type having stationary parallelplates and movable pa'rallel plates adapted to enter between thestationary plates, a movable condenser member comprising a carryingcore,parallel plates forming afi integral homogeneous body with said core,and a spindle secured to said core.

3. In an electric condenser of the type having stationary parallelplates and movable parallel plates adapted to enter between thestationary plates, a movable condenser member comprising a carrier andparallel plates forming an integral homogeneous body with said carrier,and a stationary condenser member having a metal body which comprises asintegral parts, a plate carrier and distance pieces, and separate platesset between the distance pieces of said body.

4. In an electric condenser of the type having parallel plates, acondenser member or electrode comprising a series of parallel plates anda carrier for said plates, the ma: terial constituting said plates andcarrier being formed as a single body.

5. An electric condenser comprising stationary parallel plates andmovable parallel plates adapted to enter between the stationary plates,the edges of the movable plates being arranged in step-like fashion tosecure a more gradual change of capacity.

6. An electric condenser comprising a base plate, posts risingtherefrom, a cover, a stationary condenser member depending from saidcover to within a distance from the base plate and provided withparallel plates,-a movable member journaled tightly in the cover andprovided with parallel plates adapted to enter between those of thestationary member, and a casing depending from the cover and inclosingsaid stationary member and movable member, the bottom of said casingextending between the base plate and the lower ends of said members 7.An electric condenser comprising a sup port, a stationary member securedthereto and provided with parallel plates, a movable member providedwith plates adapted to enter between those of the stationary memberandwith a spindle journaled in said spindle to engage the locking block andforce it outwardly.

8. An electric condenser comprising a support, a stationary membersecured thereto and provided with parallel plates, a movable memberprovided with plates adapted to enter between those of the stationarymember and with a spindle j'ournaled in' said support,

a' binding post connected with the stationary member, another bindingpost carried by said support but insulated therefrom, and a springcoiled around said spindle, the inner end of the spring being secured tothe spindle, while the outer end of the spring is in conductingconnection with the secon named binding post.

9. An electric condenser comprising stationary parallel lates andmovable parallel plates adapted to enter between the stationary plates,the edges of the plates of one set being arranged in step-like fashionto secure a more gradual change of capacity.

10. 'An electric condenser comprising two sets of parallel plates havingrelative mobility and adapted to overlap more or less, the edges of theplates of one set being arranged in step-like fashion to secure a moregradual change of capacity.

In testimony whereof I have signed this specification in the presence oftwo subscribin g witnesses.

GEORG SEIBT. lVitnesses:

Jorm Lo'rnA, CHARLES Martin.

